1. Field of the Invention
This invention relates to the use of mixtures of non-ionic ethylene oxide/propylene oxide adducts and anionic or cationic surfactants which are known per se as collectors for flotation processes, as aids in the flotation of non-sulfidic ores.
2. Statement of Related Art
Flotation is a separation technique commonly used in the dressing of mineral raw materials for separating valuable minerals from those with no value. Non-sulfidic minerals are, for example, apatite, fluorite, scheelite and other salt-containing minerals, cassiterite and other metal oxides, such as oxides or titanium and zirconium, and also certain silicates and alumosilicates. For flotation, the ore is subjected to preliminary size-reduction, dry-ground or preferably wet-ground, and suspended in water. Collectors are normally added to the non-sulfidic ores, frequently in conjunction with frothers and, optionally, other auxiliary reagents such as regulators, depressors (deactivators) and/or activators, in order to facilitate separation of the valuable minerals from the unwanted gangue constituents of the ore in the subsequent flotation process. These reagents are normally allowed to act on the finely ground ore for a certain time (conditioning) before air is blown into the suspension (flotation) to produce a foam at its surface. The collector acts as a hydrophobicizing agent on the surface of the minerals, causing the minerals to adhere to the gas bubbles formed during the aeration step. The mineral constituents are selectively hydrophobicized so that the unwanted constituents of the ore do not adhere to the gas bubbles. The mineral-containing foam is stripped off and further processed. The object of flotation is to recover the valuable mineral in the ores in as high a yield as possible while at the same time obtaining a high enrichment level.
Anionic and cationic surfactants are used as collectors in known flotation processes for non-sulfidic ores. Known anionic collectors are, for example, saturated and unsaturated fatty acids, particularly tall oil fatty acids and oleic acid, alkyl sulfates, particularly alkyl sulfates derived from fatty alcohols or fatty alcohol mixtures, alkyl aryl sulfonates, alkyl sulfosuccinates, alkyl sulfosuccinamates and alkyl lactylates. Known cationic collectors are, for example, primary aliphatic amines, particularly the fatty amines derived from the fatty acids of vegetable and animal fats or oils, and also alkyl-substituted and hydroxyalkyl-substituted alkylene diamines and water-soluble acid addition salts of these amines.
By virtue of their surfactant character, many collectors for non-sulfidic minerals themselves develop a foam suitable for flotation. However, it may also be necessary to develop or suitably modify the foam by special frothers. Known flotation frothers are C.sub.4 -C.sub.10 alcohols, polypropylene glycols, polyethylene glycol or polypropylene glycol ethers, terpene alcohols (pine oils) and cresyl acids. If necessary, modifying reagents, such as for example pH regulators, activators for the mineral to be recovered in the foam or deactivators for the unwanted minerals in the foam, or dispersants, are added to the flotation suspensions (pulps).
In contrast to anionic and cationic surfactants, nonionic surfactants are not often used as collectors in flotation. In Trans. Inst. Met. Min. Sect. C., 84 (1975), pp. 34-39, A. Doren, D. Vargas and J. Goldfarb report on flotation tests on quartz, cassiterite and chrysocolla which were carried out with an adduct of 9 to 10 moles of ethylene oxide with octyl phenol as collector. Combinations of ionic and nonionic surfactants are also occasionally described as collectors in the relevant literature. Thus, A. Doren, A. van Lierde and J. A. de Cuyper report in Dev. Min. Proc. 2 (1979), pp. 86-109 on flotation tests carried out on cassiterite with a combination of an adduct of 9 to 10 moles of ethylene oxide with octyl phenol and an octadecyl sulfosuccinate. In A. M. Gaudin Memorial Volume edited by M. C. Fuerstenau, AIME, New York, 1976, Vol. I, pp. 597-620, V. M. Lovell describes flotation tests carried out on apatite with a combination of tall oil fatty acid and nonyl phenyl tetraglycol ether.
Cationic, anionic and ampholytic collectors are used for the flotation of non-sulfidic ores. In many cases, collectors such as these used in economically reasonable quantities do not lead to satisfactory recovery of the valuable minerals. In order to make flotation processes more economical, it is desireable to find improved collectors with which it is possible to obtain either greater yields of valuable minerals for the same quantities of collector or the same yields of valuable minerals for reduced quantities of collector.